Integral laminated cathode and support structure



Dec. 31; 1968 o. R. KERSTETTER 3,419,744

" INTEGRAL LAMINATED CATHODE AND SUPPORT STRUCTURE Original Filed Aug. 1'7, 1964 I I/ 1/ III I! II III/Ill I w]! l I 11/ Bo/vo A/v OUTER METAL LAM/NA 72 A SEAMLESS MfTAL TUBE To PROV/DE A LAMINATED METAL CORE (0A1 5ELC TED PORT/0N5 of 00m? LAM/NA h m/ Ac/D [NSOLUBLE ZAYfR 5 [MMERSE [0R5 [N Am. BATH To DISSOLVE UNCOATED OUTER LAM/NA l [MMERSE Can-[N SOLVENT BAT/4 T0 REMOVE Ac/D [IX/SOLUBLE LAYER MENTOR I Dwvnw R KERSTETTER APPLY PaTEA/T/ALLY EM/ss/VE BY MATERIALS 7?) 00m? METAL LAM/N4 .fiyM 7.1M

ATTORNEY United States Patent 3,419,744 INTEGRAL LAMINATED CATHODE AND SUPPORT STRUCTURE Donald R. Kerstetter, Emporium, Pa., assignor to Sylvania Electric Products Inc., a corporation of Delaware Continuation of application Ser. No. 390,079, Aug. 17, 1964. This application Feb. 27, 1967, Ser. No. 619,073 3 Claims. (Cl. 313-346) ABSTRACT OF THE DISCLOSURE A laminated tubular core includes an inner lamina and first and second spaced outer lamina portions with a potentially emissive material layer affixed to the surface of the first spaced outer lamina portion to provide a cathode and the inner lamina and second spaced outer lamina portion formed to provide an attachable support structure.

This invention relates to an integral cathode and support structure and a process for fabricating such structures and more particularly to an integral cathode and support structure suitable for use in an indirectly heated electron discharge device and fabricated from a laminated metal core.

This application is a continuation application of Ser. No. 390,079 filed Aug. 17, 1964, now abandoned.

The known pencil type electron discharge devices include a cathode and support structure which is essentially a pair of co-axially aligned sleeves joined together at one end with the opposite end of the support attached to and upheld by a support member. The cathode is usually a metal sleeve of a material having high heat conductivity, good weldability to other metals, and good emission effects on potentially emissive materials while the support is a metal sleeve of a material having low heat conductivity, poor weldability to other metals, and poor emission effects on potentially emissive materials.

Although such cathode and support structures have enhanced the fabrication of pencil type discharge devices, it has been found thatthe structure leaves much to be desired because of certain inherent characteristics. For example, the purpose of the support sleeve is to properly locate and uphold the cathode sleeve which necessitates a material having good mechanical strength and rigidity. Also, the support sleeve should have alow heat conductivity and a minimum wall thickness, consistent with the desired rigidity and strength, in order to prevent undue drainage of heat from the cathode sleeve. Further, the support sleeve should have good weldability to other metals in order to facilitate the attachment thereof to a support member and to the cathode sleeve.

However, it has been found impractical to fabricate a seamless support structure from material having the abovedescribed characteristics because of the necessity of having a very thin-walled structure in order to prevent the abovementioned drainage of heat from the cathode structure. As a result, the known support sleeves have a welded seam whereat the material thickness is doubled and which tends to cause an uneven distribution of heat and inherent warpage of the structure.

Also, the cathode and support structure are usually affixed by telescoping the end of one sleeve over the end of another and welding the sleeves together. It has been found that the thinness of the wall of the support sleeve is again limited because of the need for sufiicient material to permit a welding operation. Further, the seam in the support sleeve complicates the welding process; and more importantly, the process is expensive and obtaining a true co-axial alignment of the support and cathode sleeves is not only difiicult but also impractical.

Additionally, the burrs and slivers inherent to a welding process present a multitude of problems to an operator attempting to insert a heater into a co-axially aligned and welded cathode and support structure. Moreover, the attachment of the prior known support structures to a support member requires vacuum conditions in order to provide a reliable jointure, and such a requirement is obviously expensive and inconvenient in both apparatus and labor.

Therefore, it is an object of this invention to provide an improved integral cathode and support structure for an indirectly heated electron discharge device.

Another object of the invention is to enhance the coaxial alignment of a cathode and support; structure suitable for use in an indirectly heated electron discharge device.

Still another object of the invention is to improve the means for attaching an integral cathode and support structure to a support member.

A further object of the invention is to facilitate the loading of a heater into a cathode and support structure.

A still further object of the invention is to provide an improved integral cathode and support structure fabricated from a laminated core.

An additional object of the invention is to provide a process for fabricating an improved integral cathode and support structure from a laminated core.

These and other objects are achieved in one aspect of the invention by a laminated metal core having a tubular inner lamina and an outer lamina bonded thereto. The outer lamina has spaced first and second portions with a layer of potentially emissive material adhered to the first portion and the second portion formed for attachment to a support member. In the fabrication process a tubular inner lamina is clad with a metal outer lamina to provide a laminated core. The laminated core is fabricated into an integral cathode and support by masking a portion of the outer lamina, etching away the unmasked outer lamina, removing the masking, and applying a layer of potentially emissive materials to a portion of the remaining outer lamina.

For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIG. 1 is an elevational view of a pencil type electron discharge device wherein is included an integral cathode and support structure;

FIG. 2 is an enlarged elevational view of the integral cathode and support structure of FIG. 1; and

FIG. 3 is a flow chart illustrating a process for fabricating the integral cathode and support structure of FIG. 2.

Referring to the drawings, FIG. 1 illustrates a pencil type electron discharge device 5. The device 5 includes an insulator 7, of a material such as glass, for example, a grid electrode assembly 9 sealed into and passing through the insulator, a tubular metal anode assembly 11 sealed to one end thereof, and a tubular metal cathode assembly 13 sealed to the opposite end of the insulator 7.

The grid electrode assembly 9 includes a disc 15 of a metal such as silver-plated copper which is hermetically sealed to and passes through the insulator 7. The disc 15 has an annular wall 17 defining a central aperture 19 and a cylindrical-shaped grid 21 is attached at one end to the wall 17 of the disc 15 and extends upwardly therefrom. Thus, the disc 15 which extends outwardly from the insulator 7 provides a readily available means for external electrical connection to grid 21.

The anode assembly 9 includes a tubular metal anode electrode 23 hermetically sealed to one end of the insulator 7 and an off-set section 25 surrounding the grid 21 and longitudinally limited by the disc 15. Also, an exhaust tubulation 27 of a material such as copper is disposed and sealed within the electrode 23 to provide a means for evacuating the discharge device 5. This tubulation 27 is subsequently pinched off at a point 29 to effect a hermetic seal after the above-mentioned evacuation of the discharge device has been provided.

The cathode assembly 13 includes a tubular metal cylinder 31, a glass stem member 33, a metal sleeve 35, and an integral cathode and support structure 37. The metal cylinder 31 has one end thereof hermetically sealed to one end of the insulator 7 and the opposite end of the cylinder 31 is hermetically sealed by the stern member 33 sealed thereto and disposed therein.

The glass stem member 33 includes a plurality of electrical conductors 39 sealed therein and extending therethrough to provide a convenient means for connecting an external electrical source to elements within the discharge device 5. Also, metal sleeve 35 is located within and frictionally engages the tubular metal cylinder 31 and in co-axial alignment with the stern member 33. The sleeve 35 includes an end member 41 having an annular wall 43 defining a central aperture 45.

Upheld by the sleeve 35 is an integral cathode and support structure 37 of the type commonly referred to in the electron tube art as an indirectly heated cathode. The structure 37 has one end thereof fixedly attached to the annular wall 43 of the end member 41 and extends upwardly through the aperture 45 and through the central aperture 19 of the disc and within the grid 21 of the grid electrode assembly 9. As is common for indirectly heated cathodes, an insulator covered heater 47 is disposed within and extends from the structure 37 The heater 47 has a pair of legs 49 whereon the insulation has not been included or, if included has been removed, and these legs 49 are welded or attached in some manner to the conductors 39 of the stem member 33 to permit external electrical energization of the heater 47.

As more clearly illustrated in the exploded view of FIG. 2, the integral cathode and support structure 37 includes a laminated metal core 51 having a continuous tubular metal sleeve 53, also referred to as the inner lamina, and spaced first and second outer metal lamina portions 55 and 57 bonded thereto. The first outer metal lamina portion 55 has a layer 59 of potentially emissive materials surrounding and adhered thereto and the second outer metal lamina portion 57 is bonded to the sleeve 53 and formed into a flared configuration as will be explained hereinafter.

The metal sleeve 53 with the first outer metal lamina portion 55 bonded thereto and the layer 59 of potentially emissive materials adhered to the lamina portion 55 forms a cathode section 61. Also, the metal sleeve 53 with the second lamina portion 57 bonded thereto forms a support section 63. Moreover, the heater 47 is designed and disposed within the metal core 51 in a manner such that a major portion of the energy therefrom is available at the cathode section 61.

As to materials, the tubular metal sleeve 55 or inner lamina is of a material having low heat conductivity, high mechanical strength, poor attachability to other metals, poor emission effects on potentially emissive materials, and poor solubility in an acid bath. For example, a material having a nickel to chromium ratio of about 80:20, such as Tophet A available from the W. B. Driver Company of Newark, N]. or Nichrome 5 available from the Driver Harris Company of Harrison, N.J., is preferred. However, other materials are equally applicable and appropriate so long as the above-mentioned characteristics are either present or readily obtainable.

The first and second outer metal lamina portions 55 and 57 are of a material having a relatively high heat conductivity, a relatively low mechanical strength, a relatively good attachability to other metals, a relatively good emission effect upon potentially emissive materials, and a relatively good solubility in an acid bath. Thus, nickel metals and alloys are a preferred material for the outer lamina portions 55 and 57 although other metals having the above-enumerated desirable characteristics are equally applicable and appropriate.

Additionally, the layer 59' of potentially emissive materials may be any one or a combination of materials normally used to provide a source of electrons for electron discharge devices. For example, a preferred material is a mixture of alkaline earth carbonates suspended in a suitable volatile binder and adhered to the first outer lamina portion 55 by any of a number of methods well known in the art.

As to the reason for the previously mentioned flared portion of the metal sleeve 53 and second outer lamina portion 57, it is to be noted that the outer lamina portion 57 is of a material having good attachability to other metals. Thus, this attachability feature provides a convenient means for fixedly attaching and upholding the integral cathode and support structure 37. For example, the structure 37 may be threaded through the aperture 0f the end member 41 until the second outer lamina portion 57 is brought into contact with the annular wall 43 of the end member 41. Thereupon, a welding electrode is brought into contact with the fiared end of the sleeve 53 whereby the outer lamina portion 57 is fixedly attached to the wall 43 of the end member 41 at a minimum of cost, apparatus, and inconvenience.

Referring to the flow chart of FIGURE 3, there is illustrated a preferred process for fabricating the abovedescribed integral cathode and support structure 37. Therein, a continuous tube or inner lamina of seamless material having the characteristics of the previously described metal sleeve 53 has bonded thereto by cladding, plating, or any one of numerous well-known techniques for bonding metals, an outer lamina of a material having the characteristics of the above-mentioned first and second spaced outer lamina portions and 57. Then the continuous tube of seamless material and the bonded outer lamina are drawn to a desired diametrical dimension and wall thickness, cut to a desired length, and flared at one end in a manner Well known in the art.

A portion of the outer metal lamina is then masked with a coating which is insoluble in an acid bath and the structure immersed in the acid bath. Therein, the unmasked portion of the outer lamina is dissolved to provide the spaced first and second outer lamina portions 55 and 57 and the seamless tube 53 is substantially unaffected.

Thereafter, the structure is immersed in a solvent bath wherein the coating, which served as a mask for the outer lamina in the acid bath, is removed. As a result, there is provided a seamless and continuous tubular sleeve 53 having spaced first and second outer lamina portions 55 and 57 bonded thereto. Following, a layer 59 of potentially emissive materials is adhered to the first outer lamina portion 55 in a manner well known in the art for adhering potentially emissive materials.

As a specific example of the fabrication of an integral cathode and support structure 37, a continuous tube of seamless material known as Tophet A and having a nickel-chromium ratio of :20 was clad with an ordinary nickel alloy commonly used as cathode material in electron discharge devices. The tube and alloy were drawn, in an ordinary manner, to a diameter of about 45 mils and the alloy had a thickness of about 1.5 mils. Obviously, the thickness of the tube and of the outer lamina may be varied to suit the ultimate use of the structure, and a tube or inner lamina thickness in the range of about 0.2 to 1.0 mil with an outer lamina thickness in the range of about 0.5 to 2.5 mils is preferred for integral cathode and support structures suitable for use in electron discharge devices.

A portion of the outer lamina was masked with a coating usually referred to as a stop-01f lacquer, as for example Rack Coating 218X available from the United Chromium Division of the Metals & Thermite Corpora' tion of Carteret, NJ. Then the tube and bonded outer lamina with the adhered coating thereon was immersed in an acid bath, such as a nitric acid bath for instance, wherein that portion of the outer lamina not covered by the coating was dissolved.

Thereafter, the tube and bonded outer lamina with the adherent coating thereon was immersed in a solvent for the coating, acetone in this example, wherein the coating was removed and there remained the tubular sleeve 53 and the spaced first and second outer lamina portions 55 and 57 bonded thereto. Following, a layer 59 of potentially emissive-.materials, such as a mixture of alkaline earth carbonates suspended in a volatile binder, was adhered to the first outer lamina portion 45 in a manner well known in the art to provide an integral cathode and support structure37.

It is to be noted that the integral cathode and support structure 37 fabricated in accordance with the abovedescribed method has numerous advantages which heretofore have been unobtainable. For example, the application of an outer lamina to a seamless inner lamina and the drawing of this laminated core to a desired diametrical size having a wall thickness which includes a predetermined inner lamina and outer lamina thickness ratio is believed to be unobtainable by any other process.

Further, warpage of the support structure due to unevenly distributed heat therein caused by the double seam thickness is virtually eliminated by the above-described seamless structure. Moreover, the provision of an integral cathode and support structure has permitted a reduction in the wall thickness of the support by eliminating the necessity of a Welded jointure therebetween. Also, the elimination of the weld jointure has not only enhanced the coaxial alignment of the cathode and support structure but also practically eliminated the problems previously encountered in attempting to insert a heater within the structure.

Additionally, the integral cathode and support structure has not only reduced the number of parts on inventory, the cost of assembly, and the apparatus required for assembly, but also has increased the reliability and reduced the cost of attaching the support structure to a support member by providing thereon an outer lamina having good Weldability to other metals and specifically formed for ease of attachment to a support member.

While there has been shown and described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.

I claim:

1. In an electron discharge device, an integral cathode 5 and support structure comprising in combination:

a seamless tubular core member formed. from a metal having a nickel-chromium ratio of about 80:20; said core having av thickness in the range. of about 0.2 to 1.0 mil,

an outer lamina bonded to said core member, said outer lamina having first and second axially spaced portions surrounding said core member and selected from the metal group consisting of nickel and alloys thereof, and

coating of potentially emissive materials aflixed to and surrounding said first axially spaced portion of said outer lamina whereby said core member is for-med from a metal characterized by relatively low heat conductivity, high mechanical strength, poor attachability to other metals, poor solubility in an acid bath, and a poor effect upon emissive coating as compared with said metal of said outer lamina.

2. The integral cathode and support member of claim 1 wherein said outer lamina has a thickness in the range of about 0.5 to 2.5 mils.

3. The integral cathode and support member of claim 1 wherein said second axially spaced portion of said outer lamina and said seamless tubular core bonded thereto are formed for attachment to a support member.

References Cited UNITED STATES PATENTS 948,926 2/1910 Ladofl 313*311 2,697,130 12/1954 Korbeiak 313 355x 3,092,749 6/1963 Millis 313-311 2,878,410 3/1959 Millis 313-346. 2,965,793 12/1960 Feaster et al. 3l3346 3,005,926 10/1961 Horneret a1 313-346X 3,090,733 5/1963 Brown 29 183.5X 3,116,981 1/1964 Sayre 29-1835 3,127,537 3/1964 Horsting 313-346 3,170,772 2/1965 Sato etal 29 183.5

FOREIGN PATENTS 926,845 5/1963 Great Britain. 432,484 12/1934 Great Britain. 684,891 4/19 4 Canada. 1,350,080 12/1963 France.

JOHN W. HUCKERT, Primary Examiner.

A. J. JAMES, Assistant Examiner.

U.S. Cl. X.R. 

